postfix-policyd-spf-perl: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/sbin/postfix-policyd-spf-perl - from package: postfix-policyd-spf-perl

You may install the required package with command apt-get install {package}

Error in other languages:
postfix-policyd-spf-perl: bevel nie gevind nie
postfix-policyd-spf-perl: comandă negăsită
postfix-policyd-spf-perl: comando não encontrado
postfix-policyd-spf-perl: commande introuvable
postfix-policyd-spf-perl: command not found
postfix-policyd-spf-perl: käsku ei ole
postfix-policyd-spf-perl: không tìm thấy lệnh
postfix-policyd-spf-perl: komanda nerasta
postfix-policyd-spf-perl: Kommando nicht gefunden.
postfix-policyd-spf-perl: kommandot finns inte
postfix-policyd-spf-perl: komut yok
postfix-policyd-spf-perl: nie znaleziono polecenia
postfix-policyd-spf-perl: níor aimsíodh an t-ordú
postfix-policyd-spf-perl: no se encontró la orden
postfix-policyd-spf-perl: no s'ha trobat l'ordre
postfix-policyd-spf-perl: opdracht niet gevonden
postfix-policyd-spf-perl: parancs nem található
postfix-policyd-spf-perl: perintah tidak ditemukan
postfix-policyd-spf-perl: príkaz nenájdený
postfix-policyd-spf-perl: příkaz nenalezen
postfix-policyd-spf-perl: команда не найдена
postfix-policyd-spf-perl: командата не е открита
postfix-policyd-spf-perl: 命令找不到
postfix-policyd-spf-perl: コマンドが見つかりません